Fixed #11302 -- Avoid unnesscary (and possibly unintentional) queries/results...

Fixed #11302 -- Avoid unnesscary (and possibly unintentional) queries/results from generic inline formsets.

When an instance with no primary key value is passed in to a generic inline
formset we ensure no queries/results occur. Thanks Alex Gaynor.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10981 bcc190cf-cafb-0310-a4f2-bffc1f526a37